In 1991 the International Agency for Research on Cancer (IARC) classified hot mate as carcinogenic and put it in risk category 2A, the group that includes foods and products "probably carcinogenic to humans."
According to BBC Mundo, which had access to the corresponding IARC report, several studies were carried out in the 1990s that revealed the risk of cancer for those who drink the hot yerba mate infusion.
However, they do not specify how mate is so dangerous.
Three control studies in South America investigated the relationship between mate and esophageal cancer. One of the studies, carried out in Uruguay, showed that "those who drink a lot of mate were about ten times more likely to develop cancer than people who do not drink mate," the report states.
The experts who carried out these investigations concluded that mate consumption and upper gastrointestinal cancer "suggest a strong association."